I'm out of it today, but I hope this post helps some:
1) I'm not aware of a Facebook or Google+ profile for TASVideos, but there is an
official YouTube channel that uploads encodes of all the records on the site (that each have their own comment sections), and RSS feeds for submissions as well as publications. I'm not sure if you were aware of these, but they provide a good announcement system for new runs already.
2) The IRC channel at #tasvideos is where people talk about TASes all the time. Also, like the RSS feeds, new submissions and publications are announced there. Regarding watching runs, links to WIPs and movie files can be posted in the chat too.
3) One of the main problems with paying people to TAS (from what I understand) is that usually only the TASer knows how optimized it is. A monetary reward for finishing a run will result in the runner doing low quality work or even hiding lots of possible optimizations within a run just to get the money quickly.
4) While that seems like a good idea at first, it doesn't fit the goal of the site to provide record times of runs that have been at least mostly optimized. If you want to make an unoptimized run, you can always upload it to YouTube. Otherwise, if you want to make the effort to optimize it, you can do so and then submit the result to the site.
